Physics

Hitting the Perfect Drive

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Science  04 Jun 2010:
Vol. 328, Issue 5983, pp. 1209
DOI: 10.1126/science.328.5983.1209-c

Distance and accuracy are the twin goals of a good golf drive. On a shorter course, hitting noble gas atoms with intense infrared laser pulses can produce high harmonic light of extreme UV and soft x-ray wavelength. Control of this process—which involves transient liberation of an electron from the atom, followed by dramatic energy release upon their recollision—allows the generation of attosecond light pulses with tunable wavelength (energy). However, driving the atoms in just the just right way is key to achieving the desired output shot, in terms of wavelength and duration. Hit too hard and the atom rings out with a series of harmonics that run away (group delay dispersion), which makes it difficult to exert any control over construction of the pulses; drive too softly (with subthreshold pulses) and you get the control but don't reach the energy you want. Power et al. show that a temporal characterization technique can help to provide control over the process, so that subthreshold pulses can be used to generate harmonics up to higher energy. Driving the atoms in a soft but controlled manner should allow delivery of perfect, or least improved, attosecond pulses.

Nat. Photon. 4, 10.1038/nphoton.2010.38 (2010).

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